Service chaining is a networking concept that allows for a single packet to visit sequentially multiple destinations before reaching its final destination. The method is often used for security purposes (firewall, parental control, load-balancing) but can also be used in content delivery networks for visiting different levels of caches, which can be called content hunting. It can be achieved at layer 2 using NSH or MPLS segment routing, or at layer 3 using IPv6 segment routing.
With IPv6, the destinations are encoded as a list of IPv6 destinations which are sequentially visited before reaching the final destination or, in the case of content hunting, before one of the intermediate destinations intercepts the request and serves the content. But using 128 bits per visited node is not practical when the list of destinations grows.